The method of velocity of elastic waves hodograph, aimed at non-destructive testing of structurally heterogeneous composite materials and products based on them, as well as multilayer products and constructions, is considered. The theoretical basis for determining the propagation velocity of elastic waves in a multilayer medium by the hodograph method is given. Based on the studies, recommendations are given for determining the propagation velocity of elastic waves in each individual layer of a multilayer medium, which allows non-destructive testing of the physicomechanical characteristics of each layer of a multilayer medium. It is shown that in addition to simple multiple reflections in a homogeneous medium, in a multilayer medium with parallel interfaces consisting of two or more layers, complex types of multiple reflected waves and mixed waves (reflected-refracted and refracted-reflected) can arise. The main task of applying the low-frequency ultrasonic method is to determine the acoustic parameters of the propagation of elastic waves (velocities, amplitudes, spectra). The main methods for determining the elastic wave velocities are considered, based on the hodograph equation of the indicated reflected waves in a multilayer medium.
In mining machinery, details and products made of composite materials are widely used, especially from GRP (glass-reinforce plastic). The work evaluates the relationship between the strength and the speed of ultrasound for nondestructive testing of strength in an article made of composite materials such as GDR with the use of a pulsed ultrasonic method. Methods for estimating the connection, the method of mechanical compression tests and mathematical processing and establishing the relationship between the ultrasonic velocity and the strength of GRP are considered. The results of experimental studies on establishing the relationship between the strength of GRP on compression and the speed of longitudinal ultrasonic waves are presented. As a result of statistical processing of the experimental results, equations of the relationship between the compressive strength and the ultrasonic velocity in fiberglass are obtained.
The technique of nondestructive control of anisotropy of composite materials in a product us-ing a pulse ultrasonic method is considered in the article. Calculated dependence to determine the degree of filler orientation in a polymeric composite material with varying filler laying is shown. The following filler laying is considered: chaotic, longitudinally cross, unidirectional. In addition, experimental results of anisotropy control of the elastic modulus in glass-reinforced plastics with different degrees of anisotropy using the pulsed ultrasonic method are given in the article.
The existing methods of diagnostic of destruction of the frozen basis of facilities are esteemed at straight thawing. Is marked, that the detecting of a beginning of destruction of a frozen ground can implement a а-emission method (AE). The principles of construction of diagnostic systems are reviewed, which one should consist of units of a method (reception, acceptance), transfer (transmission) and data processing. With the purpose of a reliability augmentation of diagnostic it is offered to conduct measurements AE only in narrow temperature ranges, dangerous concerning straight thawing. The statement of аemission sensors on loadbearing elements allows to use an offered diagnostic system for fracture control of concrete designs and to forecast destruction long before approach of distresses.
Specific features of technological processes of manufacturing carbon-fiber-reinforced constructions can cause non-observance of proportions of a reinforcing material and binding, a de-viation of wall thickness, porosity and rupture of threads. Difficult service conditions can lead to internal volume stratifications and formation of cracks. Above told defines necessity of carrying out of complex control of carbon-fiber-reinforced constructions at all stages of their life cycle. It is expediently to use the Eddy Current NDT for that purposes. The device with set of Eddy Current Phase and Eddy Current Frequency transducers have been developed for measurement electro-conductivity and wall thickness of constructions, detection of cracks and internal volume stratifications, and also their depth and the area. Principles of calculation and optimization of parameters of transducers, influence suppression of stirring parameters are considered.
The state of the environment in St. Petersburg has been analyzed. The factors responsible for the deterioration of environmental quality have been identified. There is practically no unified regional system of environmental quality management, the level of environmental control and environmental monitoring is low. The system of new quality indicators based on the use of the system of environmental indicators and environmental quality indices is proposed. The main feature of the proposed system of indicators is a good compatibility of indicators with the requirements put forward by decision-making systems, namely the ease of interpretation and the possibility of making decisions on the basis of these indicators. Recommendations for the creation of regional environmental quality management system have been developed.
An analysis of the state of the environment in St. Petersburg was carried out. The factors responsible for the deterioration of environmental quality have been identified. The system of new quality indicators, based on the use of a system of environmental indicators and indices of environmental quality, the feature of which is a good compatibility of indicators with the requirements put forward by the decision-making systems, is proposed.
